Maybe I should have mentioned that I use some equipment to make that difference visible. With the naked eye you cannot see it.

Let's see, for most X5 wheel/tire combos, the wheel diameter is about 74 cm. Radius is therefore 37cm. 3% of 37 is 1.1cm just under 1/2". (Since the circumference is pi * diam the 3% is linear.)

The typo is not that far off for the X5 tho and not too bad for the X3 either. In inches 29"*3.14*3% ~= 2.7 inches. So about 3" is not too far from 3%. IIRC, the tire for an X3 is 27 inches", that would make the delta for circumference about 2.5 inches.